1. Field of the Invention
The present invention relates to automatic electrode shaping apparatus for shaping electrode tips attached to the tips of arms of a welding machine, with a grinding tool.
2. Prior Art
In a conventional automatic electrode shaping apparatus, electrode tips attached to the tips of arms of a welding machine (hereinafter referred to as the arms) have been shaped with a grinding tool under rotation which comes in contact with the electrode tips. However, when the electrode tips are attached as fitted to the shanks of the arm tips, the electrode tips are vibrated during grinding so that the machining condition during grinding (hereinafter referred to as the grinding condition) easily becomes unstable, or the electrode tips become idle with respect to the shanks. This disadvantageously leads to insufficient grinding or decrease in grinding accuracy.
After the completion of grinding and shaping of electrode tips once used for welding, the machining accuracy of the point diameters of the electrode tips have been conventionally checked visually by the operator or mechanically with slide calipers or the like. In this connection, there has been conventionally disposed, adjacent automatic electrode shaping apparatus, a judging device for judging whether the shaping condition of the electrode tips is good or bad, and all electrode tips after shaped have been moved for inspection, one by one, to the position opposite to this judging device. However, since the electrode tips are attached to the tips of the arms of a welding machine, it is required to move the electrode tips after shaped, to the judging device by the rotation of the arms. It has been therefore difficult to accurately locate the electrode tips in a predetermined position with respect to the judging device. There has often occurred errors in positional relation between the judging device and the electrode tips due to the poor operating ability or accuracy of a robot which rotates the arms. There have been instances where an erroneous judgement is made; for example, an electrode tip having a point diameter greatly deviated from the reference value is judged good, or a good electrode tip is judged defective. The distances between each electrode tip and a workpiece at a time of welding are numerically controlled based on the reference value above-mentioned. Accordingly, if the erroneous judgment as above-mentioned has been made, the distances between a workpiece and shaped electrode tips to be used for spot welding cannot be accurately set. The proper welding quality can therefore not be assured.